Related papers: Large-$N_c$ relations for the electromagnetic N to…
We present a unified description of elastic and transition form factors involving the nucleon and its resonances; in particular, the $N(1440)$, $\Delta(1232)$ and $\Delta(1600)$. We compare predictions made using a framework built upon a…
A covariant spectator constituent quark model is applied to study the gamma N -> Delta(1600) transition. Two processes are important in the transition: a photon couples to the individual quarks of the Delta(1600) core (quark core), and a…
The electromagnetic N-$\Delta$ transition form factors are calculated in the framework of a formally covariant constituent diquark model. As a spin-3/2 particle the $\Delta$ is assumed to be a bound state of a quark and an axial-vector…
We present a leading-order pQCD calculation of the helicity-flip $\Delta\to N\gamma^*$ matrix element $G_0$ (Coulomb quadrupole amplitude $C2$), taking into account the transverse momenta of the quarks and the contribution from the gluons.…
Models of baryon structure predict a small quadrupole deformation of the nucleon due to residual tensor forces between quarks or distortions from the pion cloud. Sensitivity to quark versus pion degrees of freedom occurs through the $Q^2$…
The $\Delta(1232) \to \gamma^\ast N$ magnetic dipole form factor ($G_M^\ast$) is described here within a new covariant model that combines the valence quark core together with the pion cloud contributions. The pion cloud term is…
In this paper a model-independent relation which holds for the long distance part of the Fourier transform of the electromagnetic form factors of the nucleon in the large $N_c$ and chiral limits is demonstrated. This relation was previously…
In the limit of large $N_c$ we first consider the $N_c$ ordering of the various parity violating $\pi, N, \Delta$ couplings. Then we derive the relations among these couplings and consistency relations from the stability of these couplings…
In this brief pedagogical overview the physical basis of the deviation of the nucleon shape from spherical symmetry will be presented along with the experimental methods used to determine it by the gamma* p -> Delta reaction.The fact that…
A parameter-free evaluation of the $N - \Delta$ electromagnetic transition form factors is carried out in a light-front constituent quark model, based on $N$ and $\Delta$ eigenstates of a mass operator which reproduces a large set of hadron…
The novel measurements of the $\gamma^\ast N \to \Delta(1232)$ Coulomb quadrupole form factor in the range $Q^2=0.04$--0.13 GeV$^2$ changed the trend of the previous data. With the new data the electric and Coulomb form factors are both in…
The electromagnetic transition form factors for the transition between the ground and excited states of nucleons are studied in the framework of the hard-wall model of AdS/QCD. The profile functions of the spinor and vector fields in the…
Electric quadrupole (E2) moments and transitions provide measures of nuclear deformation and related collective structure. However, matrix elements of the E2 operator are sensitive to the nuclear wave function at large distances and are…
We investigate the electromagnetic transition form factors of the baryon decuplet to the baryon octet, based on the self-consistent SU(3) chiral quark-soliton model, taking into account the effects of explicit breaking of flavor SU(3)…
The electromagnetic form factors of the proton are obtained using a particular realization of QCD in the large $N_c$ limit (${QCD}_{\infty}$), which sums up the infinite number of zero-width resonances to yield an Euler's Beta function…
We explore the meson cloud contribution to nucleon electromagnetic form factors in dispersion relation approach. In our calculations, experimental data on transition amplitudes for pion-nucleon scatterings are taken directly as inputs, with…
Dispersion relations allow for a coherent description of the nucleon electromagnetic form factors measured over a large range of momentum transfer, $Q^2 \simeq 0 \ldots 35$ GeV$^2$. Including constraints from unitarity and perturbative QCD,…
Using only the current empirical information on the nucleon electromagnetic form factors we map out the transverse charge density in proton and neutron as viewed from a light front moving towards a transversely polarized nucleon. These…
We present recent lattice QCD results on the electroweak nucleon to $\Delta$ transition and $\Delta$ form factors using dynamical fermion gauge configurations with a lowest pion mass of about 300 MeV, with special emphasis in the…
We show how one may define baryon constituent quarks in a rigorous manner, given physical assumptions that hold in the large-N_c limit of QCD. This constituent picture gives rise to an operator expansion that has been used to study…